In the eighteenth centuries of Thomson very little is known about atom. Thomson was the first to prove that the atom divisible into much smaller particles. He could prove the existence of one particle (electron) only in the atom. Presence of protons and neutrons and their numbers are unknown at his time. The present model of atom is based on many experimental findings like-
i) Evidence of other fundamental particles like protons and neutrons in the atom,
ii) Evidence from Rutherford experiment of a small and heavy nucleus containing protons and neutrons,
iii) Evidence for nature of the electrons from black body radiations, photo electric effect,
iv) Quantization of energy of radiations by Max Plank
v) Atomic spectral analysis for the existence of several orbitals and
vi) Schrodinger equation to understand the behavior of electrons in atom.
The vast experimental data available helped in the present understanding of atom as having a nucleus of protons and neutrons at the center of a solid sphere where the probability of electron around the nucleus is unique by their energy and orientations in space decided by four quantum numbers.